Showing papers on "Nonpoint source pollution published in 2007"

Water quality indicators and the risk of illness at beaches with nonpoint sources of fecal contamination.

Abstract: Background:Indicator bacteria are a good predictor of illness at marine beaches that have point sources of pollution with human fecal content. Few studies have addressed the utility of indicator bacteria where nonpoint sources are the dominant fecal input. Extrapolating current water-quality thresho

Incorporating variable source area hydrology into a curve‐number‐based watershed model

Abstract: Many water quality models use some form of the curve number (CN) equation developed by the Soil Conservation Service (SCS; U.S. Depart of Agriculture) to predict storm runoff from watersheds based on an infiltration-excess response to rainfall. However, in humid, well-vegetated areas with shallow soils, such as in the northeastern USA, the predominant runoff generating mechanism is saturation-excess on variable source areas (VSAs). We reconceptualized the SCS–CN equation for VSAs, and incorporated it into the General Watershed Loading Function (GWLF) model. The new version of GWLF, named the Variable Source Loading Function (VSLF) model, simulates the watershed runoff response to rainfall using the standard SCS–CN equation, but spatially distributes the runoff response according to a soil wetness index. We spatially validated VSLF runoff predictions and compared VSLF to GWLF for a subwatershed of the New York City Water Supply System. The spatial distribution of runoff from VSLF is more physically realistic than the estimates from GWLF. This has important consequences for water quality modeling, and for the use of models to evaluate and guide watershed management, because correctly predicting the coincidence of runoff generation and pollutant sources is critical to simulating non-point source (NPS) pollution transported by runoff. Copyright  2007 John Wiley & Sons, Ltd.

Improved management of agricultural drainage ditches for water quality protection: An overview

Abstract: Agricultural drainage ditches are essential for the removal of surface and ground water to allow for crop production in poorly drained agricultural landscapes Ditches also mediate the flow of pollutants from agroecosystems to downstream water bodies This paper provides an overview of the science, management, and policy of ditches Ditches provide a unique opportunity to address nonpoint source pollution problems from agriculture due to the concentration of the contaminants and the engineered nature of ditch systems A better understanding of the nature of these complex system and the technologies available and under development to improve their management will assist in the design and implementation of water quality protection programs

Local Policy Networks and Agricultural Watershed Management

Abstract: This article emphasizes the critical role of local policy networks for the implementation of agricultural watershed management and the adoption of environmental best management practices. Local networks facilitate diffusion of innovations, the development of social capital, and cultural change. All of these elements are essential for the ability of watershed management programs to successfully solve the water quality collective action problems caused by agricultural nonpoint source pollution. Analyses of survey data from 408 orchard growers in California’s Sacramento River watershed demonstrate that exposure to policy networks substantially increases the probability of adopting environmental practices. These findings have important implications for public administration and policies where implementation depends on widespread cooperation and the development of networks with public agencies. The main goal of this article is to analyze the role of local policy networks for the implementation of agricultural watershed management. Policy networks consist of interconnected actors in a policy subsystem who communicate information about policy through some social connection (Mintrom and Vergari 1998; Rogers 2003). Agricultural watershed management is designed to reduce water quality problems associated with agricultural production, and successful implementation requires widespread cooperation. We are specifically interested in testing the hypothesis that policy networks between agricultural producers and local agencies/organizations increase the rate at which producers adopt environmental ‘‘best management practices’’ (BMP) for improving water quality. Within the literature on agro-environmental policy, BMP commonly refers to agricultural practices designed to alleviate problems associated with nonpoint source pollution from agricultural runoff. For example, this article analyzes orchard growers’ use of vegetative filter strips to control irrigation and stormwater runoff into waterways. BMP adoption, which is usually one of the main implementation goals of watershed management, entails a challenging problem in cooperation. Because individual producers cannot make a large difference in overall water quality and nonpoint source pollution is

Relationship of Land‐Use/Land‐Cover Patterns and Surface‐Water Quality in The Mullica River Basin

Abstract: We describe relationships between pH, specific conductance, calcium, magnesium, chloride, sulfate, nitrogen, and phosphorus and land-use patterns in the Mullica River basin, a major New Jersey Pinelands watershed, and determine the thresholds at which significant changes in water quality occur. Nonpoint sources are the main contributors of pollutants to surface waters in the basin. Using multiple regression and water-quality data for 25 stream sites, we determine the percentage of variation in the water-quality data explained by urban land and upland agriculture and evaluate whether the proximity of these land uses influences water-quality/land-use relationships. We use a second, independently collected water-quality dataset to validate the statistical models. The multiple-regression results indicate that water-quality degradation in the study area is associated with basin-wide upland land uses, which are generally good predictors of water-quality conditions, and that both urban land and upland agriculture must be included in models to more fully describe the relationship between watershed disturbance and water quality. Including the proximity of land uses did not improve the relationship between land use and water quality. Ten-percent altered-land cover in a basin represents the threshold at which a significant deviation from reference-site water-quality conditions occurs in the Mullica River basin.

Effects of impervious cover at multiple spatial scales on coastal watershed streams

Abstract: The spatial scale and location of land whose development has the strongest influence on aquatic ecosystems must be known to support land use decisions that protect water resources in urbanizing watersheds. We explored impacts of urbanization on streams in the West River watershed, New Haven, Connecticut, to identify the spatial scale of watershed imperviousness that was most strongly related to water chemistry, macroinvertebrates, and physical habitat. A multiparameter water quality index was used to characterize regional urban nonpoint source pollution levels. We identified a critical level of 5% impervious cover, above which stream health declined. Conditions declined with increasing imperviousness and leveled off in a constant state of impairment at 10%. Instream variables were most correlated (0.77 ≤ |r| ≤ 0.92, p < 0.0125) to total impervious area (TIA) in the 100-m buffer of local contributing areas (∼5-km2 drainage area immediately upstream of each study site). Water and habitat quality had a relatively consistent strong relationship with TIA across each of the spatial scales of investigation, whereas macroinvertebrate metrics produced noticeably weaker relationships at the larger scales. Our findings illustrate the need for multiscale watershed management of aquatic ecosystems in small streams flowing through the spatial hierarchies that comprise watersheds with forest-urban land use gradients.

Evaluation of a non-point source pollution model, AnnAGNPS, in a tropical watershed

Abstract: Impaired water quality caused by human activity and the spread of invasive plant and animal species has been identified as a major factor of degradation of coastal ecosystems in the tropics. The main goal of this study was to evaluate the performance of AnnAGNPS (Annualized Non-Point Source Pollution Model), in simulating runoff and soil erosion in a 48km^2 watershed located on the Island of Kauai, Hawaii. The model was calibrated and validated using 2years of observed stream flow and sediment load data. Alternative scenarios of spatial rainfall distribution and canopy interception were evaluated. Monthly runoff volumes predicted by AnnAGNPS compared well with the measured data (R^2=0.90, P<0.05); however, up to 60% difference between the actual and simulated runoff were observed during the driest months (May and July). Prediction of daily runoff was less accurate (R^2=0.55, P<0.05). Predicted and observed sediment yield on a daily basis was poorly correlated (R^2=0.5, P<0.05). For the events of small magnitude, the model generally overestimated sediment yield, while the opposite was true for larger events. Total monthly sediment yield varied within 50% of the observed values, except for May 2004. Among the input parameters the model was most sensitive to the values of ground residue cover and canopy cover. It was found that approximately one third of the watershed area had low sediment yield (0-1tha^-^1y^-^1), and presented limited erosion threat. However, 5% of the area had sediment yields in excess of 5tha^-^1y^-^1. Overall, the model performed reasonably well, and it can be used as a management tool on tropical watersheds to estimate and compare sediment loads, and identify ''hot spots'' on the landscape.

Multi-objective modelling and decision support using a Bayesian network approximation to a non-point source pollution model

Abstract: This paper illustrates a methodology to create a multi-objective modelling system using Bayesian probability networks to emulate the behaviour of an environmental model that was originally intended for the purpose of analyzing a problem – non-point source pollution in our example. Modelling systems frequently pertain to a single domain (physical or chemical process modelling, hydrology or combinations) to simulate a process in nature such as pollution transport or the production of food or manufactured goods. Economic or other effects are treated separately, or handled in a non-interactive manner. Side-effects of agro-industrial processes, or gains/losses from production enterprises, are generally modelled separately without the ability to examine trade-offs or alternatives. Multi-objective modelling attempts to work in more than one problem domain through decision theoretical principles. Such treatments are designed to couple production and waste systems, to quantify the economic cost of remediation. This model will demonstrate such an application, from the data acquisition, model calibration to the hypothesis testing, for a non-point source pollution model. This will be combined with a simplified net revenue model based on crop rotations typically found in Southern Ontario, Canada, using realistic economic data obtained from agricultural operations similar to those found in this region. We will demonstrate that multi-year analyses are possible with such a system.

Nonpoint Source Pollution

Abstract: A comprehensive review of the research papers published in 2018 focusing on nonpoint source (NPS) pollution is presented in this review article. The identification of pollution from different sources and estimation of NPS pollution using various models are summarized in this review paper. Various innovative techniques are also examined to abate NPS pollution. PRACTITIONER POINTS: The non-point source pollution in 2018 is systematically reviewed and documented. This review evaluates and summarizes the identification, quantification, reduction, and management of NPS pollution. Future perspectives of NPS pollution research are discussed.

The cost of cleaner water: Assessing agricultural pollution reduction at the watershed scale

Abstract: Nonpoint source pollution in intensively managed agricultural landscapes is of great concern to the general population, farmers and policymakers, as it impacts local water quality and can have large downstream effects, as in the case of hypoxia in the Gulf of Mexico. In this study, we outline a methodology to simultaneously assess economic costs and water quality benefits associated with the hypothetical placement of a broad set of conservation practices. The study, performed for the Iowa Department of Natural Resources, assesses thirteen major subbasins in Iowa by interfacing economic models with the Soil and Water Assessment Tool model. The conservation practices analyzed include land set-aside, terraces, grassed waterways, contouring, conservation tillage, and a simple nutrient reduction strategy. Annual costs range from $300 to $597 million. Predicted sediment, total phosphorus (P), and nitrate decreases range from six to 65 percent, 28 to 59 percent, and six to 20 percent, respectively, relative to the baseline.

Identifying dissolved phosphorus source areas and predicting transport from an urban watershed using distributed hydrologic modeling

Abstract: [1] A reduction in surface water quality in urban watersheds due to nonpoint source phosphorus (P) loading has prompted municipalities to consider management practices to reduce P loss from landscapes. However, locating P source areas can be time consuming and expensive. Use of distributed models allows delineation of P source areas and focused management strategies. Using the spatially distributed soil moisture distribution and routing model, we adapt and validate a dissolved P (DP) loading model for application to an urban watershed, in Ithaca, New York, to identify P source areas. The model calculates DP loss separately for base flow, impervious surfaces, plant-soil complex, and fertilized areas. The load at the outlet is the sum of P loss from the four components distributed throughout the watershed. Both stream and distributed DP loss were well predicted as indicated by comparison with measured data. The model predicted the largest contribution from plant-soil complexes (36%). Impervious surfaces contributed 10% of the total load but as much as 17% in the winter. More important, the impervious surfaces increased DP losses from the adjacent areas due to runoff from the impervious surfaces saturating the soil, thus increasing runoff losses. Fertilizer contributed substantially following application but decreased rapidly thereafter, a result of conversion from soluble to insoluble P. However, fertilization increased soil P levels, and thus DP losses were higher as a whole (19%). Results demonstrate that correctly predicting the coincidence of P and runoff source areas can be a powerful tool to identify and mitigate contamination of surface waters.

The non-point source pollution in livestock-breeding areas of the Heihe River basin in Yellow River

Abstract: A GIS-based distributed soil and water assessment tools (SWAT) model was used to simulate the runoff, sediment yield and the load of the non-point source pollution in the Heihe River basin, which is a tributary and main water supply source of the Yellow River. It is a typical stockbreeding area, and its industry and agriculture are not well developed. The main pollution source of the Heihe River was livestock related non-point source pollution. With GIS and remote sensing techniques, a database of non-point source pollution in the Heihe River basin was established. The SWAT model was parameterized for this area. The pollution load and transportation rules such as nitrogen were illustrated. After several years of hard work, the situations of point source pollution were more and more accurate. This paper provided an effective way to assess and calculate the pollution load in the wide agriculture area in China. With the help of historical data formulated parameters, the non-point source load and the theory of pollution load distribution were illustrated about the Heihe River basin. In 2000, the soluble N load in this area was 1.06 × 106 kg. By the simulation, the main pollution sources were in the south east of the basin, where the pasturing areas located in the south-east of Ruoergai County and in north of the Hongyuan County.

Nutrient loads to surface water from row crop production.

Abstract: Goals, Scope and Background Eutrophication and hypoxia, which are already serious environmental issues in the Midwestern region of the United States and the Gulf of Mexico, could worsen with an increase emphasis on the use of corn and soybeans for biofuels. Eutrophication impacts from agriculture are difficult to integrate into an LCA due to annual variability in the nutrient loads as a factor of climatic conditions. This variability has not been included in many relevant energy or row crop LCAs. The objective of this research was to develop a relatively simple method to accurately quantify nutrient loadings from row crop production to surface water that reflects annual variations due to weather. A set of watersheds that comprise most of eastern Iowa was studied. Ample data describing corn-soybean agriculture in this region and nutrient loadings to the Mississippi River enabled the development, calibration and validation of the model for this particular region.

Nutrient Load Generated by Storm Event Runoff from a Golf Course Watershed

Abstract: Turf, including home lawns, roadsides, golf courses, parks, etc., is often the most intensively managed land use in the urban landscape. Substantial inputs of fertilizers and water to maintain turf systems have led to a perception that turf systems are a major contributor to nonpoint source water pollution. The primary objective of this study was to quantify nutrient (NO3–N, NH4–N, and PO4–P) transport in storm-generated surface runoff from a golf course. Storm event samples were collected for 5 yr (1 Apr. 1998–31 Mar. 2003) from the Morris Williams Municipal Golf Course in Austin, TX. Inflow and outflow samples were collected from a stream that transected the golf course. One hundred fifteen runoff-producing precipitation events were measured. Median NO3–N and PO4–P concentrations at the outflow location were significantly (p , 0.05) greater than like concentrations measured at the inflow location; however, median outflow NH4–N concentration was significantly less than the median inflow concentration. Storm water runoff transported 1.2 kg NO3–N ha 21 yr 21 , 0.23 kg NH4–N ha 21 yr 21 , and 0.51 kg PO4–P ha 21 yr 21 from the course. These amounts represent approximately 3.3% of applied N and 6.2% of applied P over the contributing area for the same period. NO3–N transport in storm water runoff from this course does not pose a substantial environmental risk; however, the median PO4–P concentration exiting the course exceeded the USEPA recommendation of 0.1 mg L 21 for streams not discharging into lakes. The PO4–P load measured in this study was comparable to soluble P rates measured from agricultural lands. The findings of this study emphasize the need to balance golf course fertility management with environmental risks, especially with respect to phosphorus.

A GIS-based groundwater travel time model to evaluate stream nitrate concentration reductions from land use change

Abstract: Excessive nitrate-nitrogen (nitrate) loss from agricultural watersheds is an environmental concern. A common conservation practice to improve stream water quality is to retire vulnerable row croplands to grass. In this paper, a groundwater travel time model based on a geographic information system (GIS) analysis of readily available soil and topographic variables was used to evaluate the time needed to observe stream nitrate concentration reductions from conversion of row crop land to native prairie in Walnut Creek watershed, Iowa. Average linear groundwater velocity in 5-m cells was estimated by overlaying GIS layers of soil permeability, land slope (surrogates for hydraulic conductivity and gradient, respectively) and porosity. Cells were summed backwards from the stream network to watershed divide to develop a travel time distribution map. Results suggested that groundwater from half of the land planted in prairie has reached the stream network during the 10 years of ongoing water quality monitoring. The mean travel time for the watershed was estimated to be 10.1 years, consistent with results from a simple analytical model. The proportion of land in the watershed and subbasins with prairie groundwater reaching the stream (10–22%) was similar to the measured reduction of stream nitrate (11–36%). Results provide encouragement that additional nitrate reductions in Walnut Creek are probable in the future as reduced nitrate groundwater from distal locations discharges to the stream network in the coming years. The high spatial resolution of the model (5-m cells) and its simplicity may make it potentially applicable for land managers interested in communicating lag time issues to the public, particularly related to nitrate concentration reductions over time.

Managing variable source pollution in agricultural watersheds

Abstract: Agricultural runoff is a major contaminant source threatening water quality in streams, lakes, and public drinking water reservoirs. Agricultural pollution control practices and programs are traditionally based on the assumption that overland flow is only generated when rainfall intensities exceed soil infiltration capacity. This paper challenges this assumption, noting that overland flow associated with agricultural pollutant transport is often physically consistent with the variable source area hydrology concept, for which overland flow is generated in parts of the landscape where the soil saturates to the surface. Incorporation of variable source area hydrology into watershed management practices reconceptualizes nonpoint source pollution as “variable source pollution,” in which pollution control efforts can be focused on relatively small hydrologically sensitive areas recognizing that the extent of these areas will vary throughout the year. There are substantial technical, economic, social, and institutional barriers to implementing strategies for managing variable source pollution partially because of massive institutional inertia of existing agroenvironmental policies and programs and best management practices. Substantial research is needed to quantify the water quality risks associated with variable source pollution, expand the capacity to identify the critical management areas, and eliminate the institutional barriers for managing variable source pollution in agricultural watersheds.

Evaluation of Three Watershed‐Scale Pesticide Environmental Transport and Fate Models1

Abstract: The U.S. Environmental Protection Agency (USEPA) Office of Pesticide Programs (OPP) has completed an evaluation of three watershed-scale simulation models for potential use in Food Quality Protection Act pesticide drinking water exposure assessments. The evaluation may also guide OPP in identifying computer simulation tools that can be used in performing aquatic ecological exposure assessments. Models selected for evaluation were the Soil Water Assessment Tool (SWAT), the Nonpoint Source Model (NPSM), a modified version of the Hydrologic Simulation Program-Fortran (HSPF), and the Pesticide Root Zone Model-Riverine Water Quality (PRZM-RIVWQ) model. Simulated concentrations of the pesticides atrazine, metolachlor, and trifluralin in surface water were compared with field data monitored in the Sugar Creek watershed of Indiana’s White River basin by the National Water Quality Assessment (NAWQA) program. The evaluation not only provided USEPA with experience in using watershed models for estimating pesticide concentration in flowing water but also led to the development of improved statistical techniques for assessing model accuracy. Further, it demonstrated the difficulty of representing spatially and temporally variable soil, weather, and pesticide applications with relatively infrequent, spatially fixed, point estimates. It also demonstrated the value of using monitoring and modeling as mutually supporting tools and pointed to the need to design monitoring programs that support modeling.

Regional Non point Source Organic Pollution Modeling and Critical Area Identification for Watershed Best Environmental Management

Abstract: In order to implement best environmental management practices in agricultural watershed, it is necessary to evaluate non point source pollution loads and identify critical watershed pollution sources, which are regional management priority missions. Nutrient related non point source pollutant inputs can increase primary production and intensify water eutrophication. Not all watershed areas are critical and responsible for high amount nutrient pollution losses. Implementation of watershed environmental prevention is required to assess pollution yields. Further more, identification of these critical areas is essential for the effective and efficient implementation of watershed best environmental management. In this study, a geographic information system based Soil and Water Assessment Tool was applied in Bahe River watershed, a part of the Yangtze River basin. Land use, soil series texture and daily rainfall data for a 10-year period (1996–2005) was used in this study. The calibrated model system was verified to estimate average annual Organic Nitrogen and Organic Phosphorus yields in these 10 years. The estimated results were also tested and optimized by statistical software. Based on 10-year average yearly Organic Nitrogen yield and Organic Phosphorus losses, critical sub-watersheds were identified. The five sub-watersheds in the north part of watershed were under more intensive pollution yield, west group sub-watersheds contributed to moderate losses, whereas other sub-watersheds fell under slight loading classes. The research outputs developed a basis for an effective watershed environmental management plan. The study revealed that the Soil and Water Assessment Tool could be applied successfully for identifying critical sub-watersheds for watershed best environmental management purposes.

Phosphorus load reduction goals for Feitsui Reservoir Watershed, Taiwan.

Abstract: The present paper describes an effort for developing the total maximum daily load (TMDL) for phosphorus and a load reduction strategy for the Feitsui Reservoir in Northern Taiwan. BASINS model was employed to estimate watershed pollutant loads from nonpoint sources (NPS) in the Feitsui Reservoir watershed. The BASINS model was calibrated using field data collected during a 2-year sampling period and then used to compute watershed pollutant loadings into the Feitsui Reservoir. The simulated results indicate that the average annual total phosphorus (TP) loading into the reservoir is 18,910 kg/year, which consists of non-point source loading of 16,003 kg/year, and point source loading of 2,907 kg/year. The Vollenweider mass balance model was used next to determine the degree of eutrophication under current pollutant loading and the load reduction needed to keep the reservoir from being eutrophic. It was estimated that Feitsui Reservoir can becoming of the oligotrophic state if the average annual TP loading is reduced by 37% or more. The results provide the basis on which an integrated control action plan for both point and nonpoint sources of pollution in the watershed can be developed.

Dry Weather Water Quality Loadings in Arid, Urban Watersheds of the Los Angeles Basin, California, USA

Abstract: Dry weather runoff in arid, urban watersheds may consist entirely of treated wastewater effluent and/or urban nonpoint source runoff, which can be a source of bacteria, nutrients, and metals to receiving waters. Most studies of urban runoff focus on stormwater, and few have evaluated the relative contribution and sources of dry weather pollutant loading for a range of constituents across multiple watersheds. This study assessed dry weather loading of nutrients, metals, and bacteria in six urban watersheds in the Los Angeles region of southern California to estimate relative sources of each constituent class and the proportion of total annual load that can be attributed to dry weather discharge. In each watershed, flow and water quality were sampled from storm drain and treated wastewater inputs, as well as from in-stream locations during at least two time periods. Data were used to calculate mean concentrations and loads for various sources. Dry weather loads were compared with modeled wet weather loads under a range of annual rainfall volumes to estimate the relative contribution of dry weather load. Mean storm drain flows were comparable between all watersheds, and in all cases, approximately 20% of the flowing storm drains accounted for 80% of the daily volume. Wastewater reclamation plants (WRP) were the main source of nutrients, storm drains accounted for almost all the bacteria, and metals sources varied by constituent. In-stream concentrations reflected major sources, for example nutrient concentrations were highest downstream of WRP discharges, while in-stream metals concentrations were highest downstream of the storm drains with high metals loads. Comparison of wet vs. dry weather loading indicates that dry weather loading can be a significant source of metals, ranging from less than 20% during wet years to greater than 50% during dry years.

Prairie and turf buffer strips for controlling runoff from paved surfaces

Abstract: Eutrophication of surface waters due to nonpoint source pollution from urban environments has raised awareness of the need to decrease runoff from roads and other impervious surfaces. These concerns have led to precautionary P application restrictions on turf and requirements for vegetative buffer strips. The impacts of two plant communities and three impervious/pervious surface ratios were assessed on runoff water quality and quantity. A mixed forb/grass prairie and a Kentucky bluegrass (Poa pratensis L.) blend were seeded and runoff was monitored and analyzed for total volume, total P, soluble P, soluble organic P, bioavailable P, total suspended solids, and total organic suspended solids. Mean annual runoff volumes, all types of mean annual P nutrient losses, and sediment loads were not significantly affected by treatments because over 80% of runoff occurred during frozen soil conditions. Total P losses from prairie and turf were similar, averaging 1.96 and 2.12 kg ha(-1) yr(-1), respectively. Vegetation appeared to be a likely contributor of nutrients, particularly from prairie during winter dormancy. When runoff occurred during non-frozen soil conditions turf allowed significantly (P < or = 0.10) lower runoff volumes compared with prairie vegetation and the 1:2 and 1:4 impervious/pervious surface ratios had less runoff than the 1:1 ratio (P < or = 0.05). In climates where the majority of runoff occurs during frozen ground conditions, vegetative buffers strips alone are unlikely to dramatically reduce runoff and nutrient loading into surface waters. Regardless of vegetation type or size, natural nutrient biogeochemical cycling will cause nutrient loss in surface runoff waters, and these values may represent baseline thresholds below which values cannot be obtained.

Development of Refined BOD and DO Models for Highly Polluted Kali River in India

Abstract: Most commonly used river water quality models for biochemical oxygen demand (BOD) and dissolved oxygen (DO) simulations are mainly based on advection, decay, settling, and loading functions. Using these concepts, refined river water quality models for BOD and DO simulations are developed in the present work considering a large number of physically based parameters and input variables. The refined models developed can be transformed to some of the commonly used river water quality models, if physically based parameters and input variables are omitted or removed. To test the applicability of the refined models developed and commonly used models, a total of 732 water quality and flow data sets are collected during March 1999–February 2000 from 22 sampling stations of the River Kali in India. River Kali is a highly polluted river in India and receives continuous inflow of untreated point source pollution from municipal and industrial wastes and nonpoint source pollution from agricultural areas. Newton–Raphson...

Co-ordinated environmental regulation : controlling non-point nitrate pollution while maintaining river flows.

Abstract: Environmental policy often addresses multiple targets, yet much economic analysis of pollution control is based on a single-target objective. In this paper, we present an analysis of policies to control non-point source nitrate pollution in the presence of minimum river flow restrictions. A non-linear bio-physical economic optimisation model of an intensively cultivated Scottish agricultural catchment was constructed. The presence of minimum river flow controls in the catchment was found to reduce nitrogen pollution. However, by themselves, river flow controls were found not to be a cost effective means to reduce non-point pollution. We quantify the improved social welfare from coordinating the environmental regulation of river flows and pollution, and determine the conditions under which such coordination is beneficial. The paper also investigates whether the benefits of such coordination can be sustained under wetter (winter) weather conditions implied by current climate change predictions.

Water Quality Modeling of Two Agricultural Fields in Southern Quebec Using SWAT

Abstract: To study the dynamics of nutrient transport at the field scale, we collected data from two tile-drained agricultural fields in the Pike River watershed of southern Quebec. A two-year data set was used to calibrate and validate the Soil and Water Assessment Tool (SWAT) for sediment, nitrate, and phosphorus loads exiting the field through surface runoff and tile drainage. We found that SWAT output on water quality required an accurate estimation of the timing and form of field management practices employed. After calibration, the monthly coefficients of performance (Cp) over four site-years varied from 0.23 to 0.89 for sediment loads, from 0.48 to 1.35 for nitrate loads, and from 0.38 to 0.67 for total phosphorus loads. Subsurface nitrate loads accounted for 97.7% and 86.7% of the total nitrate yield, while particulate phosphorus accounted for 61.2% and 87.7% of total phosphorus load on sites 1 and 2, respectively. SWAT underestimated nitrate loads in subsurface drainage during spring snowmelt and large storms. Sediments and particulate phosphorus predictions were most accurate of all simulated parameters, whereas dissolved phosphorus was marginally overestimated year-round. Overall, SWAT satisfactorily reproduced field observations for sediment and nutrient transport and could be used to compare the impacts of implementing different best management practices (BMP) on individual fields for the study site.